1. Field of the Invention
The present invention relates to a transmission type screen capable of preventing reduction in brightness in an image peripheral part, and a head-up display device using such a transmission type screen.
2. Description of Related Art
For example, a head-up display (HUD) device for vehicle projects driving information (e.g., speed display and navigation display) as a virtual image such that the virtual image is projected ahead of a front windshield relative to a driver, i.e., the virtual image is superposed on a foreground of a front viewing field. A vehicle display system using such a HUD can restrain as much as possible movement of a line of vision of a driver, when he/she observes the driving information.
In the field of the above-described head-up displays and projectors, the use of a microlens array (MLA) as a transmission type screen is proposed.
As an example of a device in which a microlens array is used as a transmission type screen, Patent Document 1 (JP2010-145745A) discloses an image forming device including: a laser projector using laser light as a light source and configured to project an image formed by an array of pixels; a microlens array in which microlenses are arrayed; a condenser lens disposed on a light path between the laser projector and the microlens array, and configured to correct an image such that an incident angle of laser light incident on each microlens is included in an angular aperture of the microlens and to project the image; and an optical system enlargement element configured to enlarge an image formed on an emitting surface of the microlens array.
Patent Document 1: JP2010-145745A